Voltage regulation arrangement for contact converters



July 14, i959 H. BLATTER 2,895,101

VOLTAGE R EGULATION ARRANGEMENT FOR CONTACT CONVERTERS Filed May 10, 1957 2 Sheets-Sheet 1 \izgg +WUWF I ATTORNEY 5 H. BLATTER July l4, 1959 I VOLTAGE REGULATION ARRANGEMENT FOR CONTACT CONVERTERS Filed May 10, 1957 2 Sheets-Sheet 2 INVENTOR M W .ATTORNEYSf United States Patent VOLTAGE REGULATION ARRANGEMENT FOR CONTACT CONVERTERS Hans Blatter, Wettingen, Switzerland, assignor to Aktiengesellschaft Brown, Boveri & Cie., Baden, Switzerland, a joint stock company Application May 10, 1957, Serial No. 658,322

Claims priority, application Switzerland May 24, 1956 4 Claims. (Cl. 321-48) In grid-controlled rectifiers of any desired type the voltage produced is changed in that during one period current is allowed to pass through the rectifier in a different region of the alternating voltage to be rectified. The highest voltage is obtained when current is allowed to pass in the region around the highest amplitude of the alternating voltage, the smallest voltage, or zero voltage, when the region lies about the zero passage of the voltage.

In electron-tube rectifiers this voltage can be changed by controlling the grids. In mechanical contact converters one cannot use a grid control, but must provide other means in order to be able to control the voltage produced. This is done either by displacing the switchmake instant of the contacts relative to the supplied alternating voltage, or by variable magnetization of the switch throttle coil connected before the contacts during the switch-make instant. In the first case the switch-make instant is displaced in such a way that the current circuit is closed only from a certain instantaneous value of the existing voltage.

The interruption of the current in all cases occurs within the weak current switch-ofi before the Zero passage of the current in the contacts. The smaller the control, the shorter the current overlap between two detaching contacts; therefore the contact duration must also be reduced. But this modification has disadvantages, since in mechanical rectifiers the modification of the contact duration can be achieved only by mechanical means.

In the second case the contact duration can remain unchanged. The switch-break current is determined by the switch throttle coil, in that it prevents the current rise in the closed contact until the desired instantaneous value of the voltage is attained. The actual purpose of the switch throttle coil is however to keep the current to a small value during the switching oil of the contacts for such a time that a sufiiciently long pause, free of current, is produced, to be able to open the contacts without current. This chief task of the switch throttle coil must not be detrimentally influenced by the premagnetization upon switching on the contacts. Therefore care must be taken that the magnitude of the positive incremental current is not influenced in the opening of the switch contacts due to the variable pre-magnetization in the switchon instant of the contacts; that is, the pre-magnetized state of the switch throttles must remain unchanged in the switch-01f instant, while the pre-magnetized state in the switch-on instant can be changed. This can be achieved in that one allows the direct current pre-magnetization to act only at the switch-on instant. Complicated wirings are needed for this, however, for example additional throttle coils and electron tubes, which make the entire arrangement more expensive.

One can also use two different switch throttle coils, one for the switch-on, the other for the switch-off, but this too produces expensive arrangements. Furthermore one can provide the switch throttle coils with two premagnetization windings, of which the one is fed with an invariable sinusoidal alternating voltage, the other with 2,895,101 Patented July 14, 1959 a variable direct voltage. In this however the magnetization state in the switch-off instant also changes with the switch-on instant, if the direct current pre-magnetization acts in the switch-off instant. Through this the magnitude of the switch-off current becomes different depending on the voltage control. This idea can therefore be realized only when it can be made possible through other means, that independently of the effective incremental current the switch-off conditions for the contact itself are not made more diflicult, that is the current actually to be interrupted by the contact always remains below a certain minimum value.

It is furthermore known to assign parallel circuits to the contacts. Through this it is achieved that the still remaining residual current changes from the contact to be switched off over to the parallel circuit, if it possesses a correspondingly small resistance precisely at the switchoif instant. Such parallel circuits can consist as known of condenser circuits or of circuits with valves.

According to the instant invention it is now proposed for contact converters having switch throttle coils, which possess one winding each for alternating current premagnetization and one for changing the variable direct current pre-magnetization of the direct voltage given off, to control at the same time with the direct current premagnetization also the valves of the parallel circuits in such a way that at the moment of opening of the contacts the current flowing through the switch throttle coil is compensated in the whole regulating region of the direct voltage by the current in the parallel circuit. This results in the advantage that the current flowing over the contacts assumes such a small value that a flawless switching is assured, without expensive additional measures, therefore that for example the current always remains below 0.5 A.

In this the alternating voltage pre-magnetization can remain unchanged, as in the known arrangements. The inventive idea can be realized for example in that the direct current pie-magnetization is fed by a regulatable direct current generator, whose voltage is introduced at the same time into the anode circuit of the parallel circuit valves as a direct anode voltage. Through this it is achieved that in changing the direct voltage at the same time with the ire-magnetization the direct anode voltage and thus the anode direct current are also changed. The voltage of the direct current generator can be so regulated in this that the adjusted voltage or the current given oif remain automatically at the same value as the network voltage changes.

The direct voltage can be produced in a generator which is driven by an alternating current motor; it can however also be produced in a rectifier transducer circuit which is fed by the alternating current network.

Instead of changing the anode voltage simultaneously with the pre-magnetization one can also influence the grid pre-voltage of the valves so that with increasing premagnetization the grid voltage changes toward the positive side and so allows the anode current to increase likewise. One can also carry out the control in such a way that the anode voltage as well as the grid pre-voltage are changed with the pre-magnetization of the switch throttle coil. This way one has still more possibilities for adapting the reciprocal dependence exactly to each other.

The simple manner of this control furthermore makes it possible not only to adjust the voltage given off in advance as desired, but one can also provide for a regula tion in dependence on the load. Thus for example one can make the voltage given otf dependent on the load current or on the power given off. For this it is necessary for example to build a direct current changer into the load circuit, which gives off the necessary regulating magnitude.

It is also expedient in this arrangement to connect the direct current source in parallel with a condenser in order to be able to lead off the alternating and impulse currents flowing in the valves.

Other objects and advantages of my invention will become more apparent from a study of the following specification when considered in conjunction with the accompanying drawings in which:

Fig. 1 is a schematic diagram of my invention provided with electron control tubes;

Fig. 2 shows an embodiment of the invention of Fig. 1 having a rectifier transducer circuit in place of the D.-C. generator;

Figs. 3-6 are diagrams illustrative of the principles of the invention.

In Figure l the transformer which feeds the contact switch is designated by the reference numeral 1. The contact switch contains three contacts 21, 22, 23 fed through the switch throttle coils 11, 12, 13 having windings a, b, c, d. The contacts are activated by the alternating current motor 2 which is fed from the alternating current network RST. The load 3 is connected in series with the contact switch. The grid-controlled valves, for example thyratrons 31, 32, 33 are connected in parallel with the switch contacts 21, 22, 23. The parallel circuits begin in front of the contacts 21, 22, 23, go through the auxiliary transformers 41, 42, 43, through tubes 31, 32, 33 through the D.-C. source 14, and through the impedance 7, which contains inductive, capacitive, and resistance components, back to the contacts. The

direct current generator is driven by the auxiliary transformer 17. It receives its regulation from the auxiliary exciting machine 15 through the resistance 10 and the rotary regulator 9.

The switch throttle coils 11, 12, 13 are pre-magnetized with constant alternating current from the alternating current network of the auxiliary transformer 17 through the throttle coil 4 and the windings b; the switch throttle coils are also premagnetized with direct current from the direct voltage 14 through the throttle coil 5 and the resistance 6 via the windings 4. The direct current premagnetization can be adjusted according to the circuit operation by means of the regulating resistance 9 as well as the variable resistance 10.

The tubes 31, 32, 33 receive an alternating anode voltage from the alternating current network of the trans former 17 through the auxiliary transformers 41, 42, 43 and according to the instant invention a supplemental direct anode voltage from the variable direct voltage source 14-.

The grids of the tubes are likewise controlled in that the voltage produced on the switch throttle coils (winding directly influences the grid through the pre-connected resistances 3 35, 36. The grid pre-voltage is developed by the direct current generator 15, which is driven by the motor 16. The regulation of the arrangement in dependence on the load current occurs from the direct current transformer 8 (shown schematically in the drawing) with the aid of the rotary regulator 9, which influences the regulation of the generator 14 in familiar manner.

A condenser 18 is connected parallel to the voltage of the generator, which absorbs impulse thrusts which may occur and thereby keeps them away from the control.

In Figure 2 the generator 14 is replaced by the rectifier transducer circuit 19, which is fed by alternating current from the secondary of the auxiliary transformer 17 at connections 51, 52, 53. The transducer is regulated by the direct current changer 8 through the serially connected windings 24.

The mode of operation of the whole arrangement may now be explained with reference to Figures 3 to 6. Figures 3 and relate to the full control of the contact converter, and Figures 4 and 6 relate to partial control. It is a prerequisite that the incremental current remains positive and as small as possible during the disconnection period. The pre-magnetization must therefore act in such a way that the switch throttle coil is desaturated in the region before the zero passage of current.

The magnetization curves of the switch throttles are presented in familiar manner in the upper part of Figures 3 and 4-. 1 shows the constant alternating voltage premagnetization proceeding sinusoidally. I represents the direct current pre-magnetization, which is adjustable.

The magnetizing currents are so chosen that the point at which the switch-make occurs lies in one case in the saturated state (P in the other case in the desaturated state (P In the fully controlled state the switch throttle coil is practically saturated during switch-make so that current can flow immediately when connected and thus the entire current curve is rectified. The switchmake in this case takes place precisely at the instant of the detaching voltages, so that no voltage is present at the contact itself. In the partially controlled state (Figure 4) the switch throttle coil is desaturated at the switch-make instant, so that the connection occurs with small current, but no current flows even after the connection, until the switch throttle coil is saturated again as a result of the supplemental state of magnetization flowing through the working winding. Therefore the premagnetization must be changed in accordance with control. This is done with the direct current pre-magnetization, which accordingly must be greater in partial control than in full control. In this manner the state of magnetization of the switch throttle becomes displaced from the point P to the point P when the contacts are switched on.

Through superimposition of the variable direct current magnetization however the state of magnetization of the switch throttle is also displaced upon disconnection, from the point P in the fully controlled state to the point P in the partially controlled state. The incremental current is therefore somewhat larger, depending on the control. In order to be able to connect the contacts practically free of current, this current must be compensated by the current in the parallel circuit.

In Figures 5 and 6 is represented the corresponding course of the switch-break current. The current in the switch throttle still does not have the value zero. In order to be able to compensate it, the parallel circuit must also carry the same current. The solid line 54- represents the current in the switch throttle coil and the line 55 delineated by shading represents the current in the parallel circuit. The magnitude of this current is adaped to the incremental current through the control of the anode voltage at the same time with the modification of the direct current pre-magnetization.

Figure 5 shows the fully controlled state and Figure 6 illustrates the partially controlled state. The direct current magnetization must be reinforced and also at the same time the current in the parallel circuit.

The advantage of the inventive concept appears clearly on the basis of these presentations. The contact time can be kept constant, through which arises a structural facilitation. Although the control of the switch-make instant must be changed for the purpose of control and in dependence on the load current, the contacts nevertheless switch practically free of current, since the remaining residual current is compensated by the current in the tubes of the parallel circuit with corresponding control.

While in accordance with the provisions of the statutes I have illustrated and described the best forms and embodiments of my invention known to me, it will be apparent to those skilled in the art that changes may be made in the form of the circuitry described without de parting from the spirit of my invention as set forth in the appended claims.

What I claim is:

1. In a contact converter system, the invention which comprises a switch throttle coil connected in series with the converter contacts, means for applying an alternating-current premagnetization control component upon said throttle coil, a control circuit connected in parallel with the converter contacts and including a grid-controlled electron tube, means for simultaneously applying a direct-current premagnetization control component upon said throttle coil and a direct-current voltage component into the cathode-to-anode circuit of said grid-controlled electron tube so that an increase in direct-current prernagnetization will be accompanied by an increase in the anode direct-current voltage, and means for applying a control signal from said throttle coil upon the grid of said electron tube to control the flow of current in the parallel circuit whereby during switching the current flowing through the contacts will assume a small value.

2. A contact converter system as defined in claim 1 wherein said means for simultaneously applying the direct-current premagnetization control component upon the throttle coil and the direct-current voltage component into the anode circuit includes a regulatable direct-current generator.

3. Apparatus as defined in claim 2 wherein the directcurrent generator is regulated as a function of the magnitude of the output voltage of the contact converter.

4. Apparatus as defined in claim 2 and further including a condenser connected in parallel across said direct-current generator.

References Cited in the file of this patent 

